349
FXUS66 KPDT 031806
AFDPDT

Area Forecast Discussion
National Weather Service Pendleton OR
1006 AM PST Wed Dec 3 2025

.MORNING UPDATE...Fog banks around the Columbia Basin have been
more persistent than forecast this morning, with short-term model
guidance not handling fog extent very well at this time. Current
thoughts are that freezing fog will persist across portions of the
Yakima valley this morning, while freezing fog will expand across
the Kittitas valley, with both areas seeing fog persist through at
least 1PM. Will reevaluate fog in those areas before in a couple
of hours. As for the Blue Mountain foothills, temperatures have
warmed just above freezing, but dense fog persists, with patchy
fog expanding into the Oregon Columbia Basin. Have issued dense
fog advisories for the northern Blue mountain foothills, which are
in effect through 3PM this afternoon. Will also reevaluate these
advisories here in the next couple hours. Otherwise, patchy fog
has been noted across portions of the eastern mountains in Oregon,
as well as around the Horse Heaven Hills. With thicker cirrus
decks building over the forecast area, expect little breakdown of
the current fog banks. Besides fog, the remainder of the forecast
area will remain dry, but cool as well.


&&

.AVIATION...18Z TAFS...Variable conditions across all sites, with
VFR at KRDM/KBDN, MVFR at KPSC, IFR at KYKM/KDLS, and LIFR at
KPDT/KALW due to reduced visibilities of 1/4 to 1/2 SM at ceilings
of 200 feet. These conditions are expected to persist into the early
afternoon before slight improvement to MVFR associated with
visibilities hovering between 4-5SM and ceilings around 2.5-3kft.

Due to the influence of the upper level ridge and northwest flow
aloft, ceilings and visibilities will again degrade this evening
into Thursday morning as fog is expected to again develop LIFR
conditions for KPDT/KALW/KYKM. Ceilings of around 1kft are likely
for KPSC overnight, but should stay MVFR. 75


&&


PREV DISCUSSION... /issued 331 AM PST Wed Dec 3 2025/

.DISCUSSION...Webcams show low visibilities across roads and
interstates across the Yakima Valley and the Foothills of the Blues.
Likely remain for the rest of the night as winds stay fairly light
with limited cloud cover over the effected areas currently. Fog and
freezing fog remain the primary story for tonight, as temperatures
continue to fall below freezing with the efficient radiation
cooling.

Mostly dry conditions will continue through Wednesday and through
Thursday night with dry northwesterly flow aloft continuing from the
offshore high pressure system (>90% confidence). Next weather system
will begin sometime in the later part of Thursday morning as a
shortwave with increased cyclonic vorticity aloft develops low
valley rain with light mountain snow (50-80% confidence).
Impacts start to increase Friday and towards the rest of the weekend
with a positively tilted trough from the providence`s of Manitoba
and Saskatchewan digs further south enough to trigger multiple short
waves across the Washington/Oregon area. Most of the main impacts
will be felt from the heavy mountain snow and potential wind events
at advisory level (20-60 percent chance across most of the region)
with strongest winds looking to occur late Friday afternoon through
mid Saturday morning. A warming trend will begin Thursday, giving
us a break from the below freezing temperatures we`ve observed the
past few days, with highs trending up into the low and mid 50s
through the weekend. Clusters are in agreement with a generally
narrative that we will continue to see valley rain and light
mountain snow/wintry mix go through mid next week, although to the
extent how strong/weak the system will be remains a bit uncertain
with Day 7 and being in the autumn generally bring great
uncertainty. NBM clusters are close to 50/50 to deliver a strong
or weak ridge system, but every member does advertise some form of
rain or wintry mix situation.


&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  41  29  42  36 /   0  10  70  70
ALW  39  31  41  36 /  10  10  80  70
PSC  38  28  40  31 /   0  10  60  40
YKM  38  28  42  29 /  10  10  40  30
HRI  39  29  41  34 /   0  10  70  50
ELN  38  27  41  30 /  10  20  40  40
RDM  45  25  47  34 /   0  10  40  30
LGD  41  26  41  36 /   0  10  80  80
GCD  42  26  43  37 /   0   0  70  80
DLS  44  37  47  42 /  10  20  70  60

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Dense Fog Advisory until 3 PM PST this afternoon for ORZ507.

WA...Dense Fog Advisory until 3 PM PST this afternoon for WAZ029.

     Freezing Fog Advisory until 1 PM PST this afternoon for WAZ026.

     Freezing Fog Advisory until 1 PM PST this afternoon for WAZ027.

&&

$$

MORNING UPDATE...82
DISCUSSION...95
AVIATION...75